1. Field of Invention
This invention relates to a flotation process, e.g., such as a flotation separation process used in a mineral extraction processing system; and more particularly to a technique for controlling such a flotation separation process.
2. Description of Related Art
In many industrial processes, a flotation separation process is used to concentrate and clean the final product. A minerals processing plant, or benefaction plant, is no exception. In the case of a copper concentrator as shown in FIG. 1a, the input to the plant is water and ore (of a particular type and size distribution) and the outputs are copper concentrate and tailings. The processes consist of grinding, classification, flotation and thickening stages, as shown in FIG. 1b. The grinding and classification stages produce a fine slurry of water, ore and chemicals which is then sent to the flotation stage. Once in the flotation stage, air and chemical reagents are used to float the copper minerals, while gange (tailings) is depressed. The recovered copper is cleaned and dried. The tailings are thickened and sent to a tailings pond.
In the flotation stage, the bubbles are introduced to the slurry to carry (float) the desired ore content to the top of the flotation cell, while the tailings are depressed and flow to the bottom of the cell. The performance of the flotation stage is dependent on many parameters. One of those is the floatability of the ore. The floatability is highly dependent on the type and doses of chemical reagents that are used to make the desired particles of ore hydrophobic. The chemical dosing rate is typically defined in units of grams of chemical per ton or ore processed. In some cases, more chemical is added than is necessary in order to make sure that enough is being used. These chemicals are very expensive and make up a sizable portion of a mineral processing plant's operational expenses.
Another factor in the performance of the flotation stage is the size of the bubbles, the overall amount of bubbles, and the rate or speed that the bubbles move/rise through the flotation cell. These bubbles create a layer of froth at the top of the flotation cell. The characteristics of the froth, such as the depth of the froth layer, its composition and its stability, also impact the performance of the flotation stage.
In a typical plant, operators will determine the ore tonnage rate by using a weight scale on the input ore feed to the first stage of grind. Then the reagent is added according to the prescribed dosing rate. It would be possible to optimize the addition of reagent and other control parameter, such as the addition of air and feed rate and density of the ore, to optimize the recovery of ore in the flotation stage.